Apparatus and method for transmitting and receiving wireless packet data

ABSTRACT

An apparatus and method for transmitting and receiving wireless packet data are provided. In a wireless packet data transmitter for transmitting to a wireless packet data receiver data packet on a transport channel and control information for supporting the transport channel on a control channel in a wireless packet data communications system, a padding bit eliminator eliminates optional padding bits of a variable size from a transport block for data packet transmission. A transport channel encoder for transport channel-encodes the transport block without the padding bits and transmits the encoded transport block on the transport channel. A control channel encoder control channel-encodes the control information including a padding bit number indicator indicating the number of the eliminated padding bits and transmits the encoded control information on the control channel.

PRIORITY

This application claims priority under 35 U.S.C. §119 to an applicationentitled “Apparatus and Method for Transmitting and Receiving WirelessPacket Data” filed in the Korean Intellectual Property Office on Dec.12, 2005 and assigned Serial No. 2005-122151, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a packet data service system,and in particular, to a wireless packet data service system in awireless mobile environment.

2. Description of the Related Art

Mobile communications systems are being developed to be high-speed,high-quality wireless packet data communications systems to additionallyprovide data service and multimedia service beyond voice-orientedservice that was available at an early development stage.

The 3^(rd) Generation Partnership Project (3GPP) standardization of HighSpeed Downlink Packet Access (HSDPA) and the 3GPP2 standardization of1×Evolution for Data and Voice (EV-DV) in Release 5 are good examples ofthe efforts to find a solution to wireless data packet transmissionservice with high quality at a high speed of 2 Mbps or above in a 3Gmobile communication system. 4^(th) Generation (4G) mobile communicationsystems aim to provide higher-speed, higher-quality multimedia service.Enhanced Uplink Dedicated Channel (EUDCH) under discussion in Release 6is also an example of one of the efforts to transmit high-speed,high-quality wireless data packets on the uplink.

Obstacles to high-speed, high-quality data service in wirelesscommunications are caused mainly by a radio channel environment. Theradio channel environment frequently changes due to signal power changesby fading as well as white noise, shadowing, Doppler effects caused byuser mobility and frequent mobile velocity changes, and interferencefrom other users and multipath signals.

To provide high-speed wireless packet data service, therefore, otheradvanced technologies than those provided in the existing 2nd Generation(2G) or 3G mobile communication systems are needed for increasing theadaptability to channel changes. Although fast power control used in thelegacy systems increases the adaptability to channel changes, the 3GPPand the 3GPP2, which are working on the standardization of high-speedpacket data transmission systems, commonly address Adaptive Modulationand Coding (AMC) and Hybrid Automatic Repeat reQuest (HARQ).

The AMC adaptively selects a modulation scheme and a coding rateaccording to the downlink channel environment. The downlink channelenvironment is evaluated based on feedback information about aSignal-to-Noise Ratio (SNR) measurement received from a User Equipment(UE), and the modulation scheme and the coding rate are determinedaccording to the downlink channel environment.

In an AMC system, a high-order modulation scheme such as 16-aryQuadrature Amplitude Modulation (16QAM) or 64QAM and a high coding ratesuch as 3/4 are selected for a good channel environment in which a UEnear to a Node B is usually situated. For a UE at a cell boundary, alow-order modulation scheme like Quadrature Phase Shift Keying (QPSK) or8-ary Phase Shift Keying (8PSK) and a low coding rate like 1/2 are used.This AMC technology reduces interference and improves system performanceon the whole, compared to the conventional fast power control.

The HARQ is a link control scheme for the case where, in the presence oferrors in an initially transmitted packet, packet retransmission isrequested to compensate for the error packet. The HARQ is broken up intoChase Combining (CC), Full Incremental Redundancy (FIR), and PartialIncremental Redundancy (PIR).

In the CC, the same packet as initially transmitted is retransmitted. Areceiver combines the retransmitted packet with the initiallytransmitted packet buffered in a reception buffer, thereby increasingthe reliability of coded bits input to a decoder and thus achieving anoverall system performance gain. Combining the same two packets isequivalent to iterative coding in effect. Thus, a performance gain ofabout 3 dB is achieved on the average.

The FIR improves decoder performance at the receiver by transmitting aretransmission packet having only redundant bits generated from achannel encoder, rather than retransmitting the same packet. As thedecoder uses both the initial transmission information and the newredundant bits, the resulting decrease in coding rate increases thedecoder performance. It is well known in coding theory that a higherperformance gain is obtained by a low coding rate than by iterativecoding. Only in terms of performance gain, the FIR outperforms the CC.

In contrast to the FIR, the PIR transmits packet data with informationbits and new redundant bits at a retransmission. At decoding, theinformation bits are combined with initially transmission informationbits, thereby achieving the same effects as the CC, and the use of theredundant bits results in the effects of the FIR. Since the PIR uses ahigher coding rate than the FIR, it performs between the FIR and the CC.However, since many considerations including system complexity such as abuffer size at the receiver and signaling, as well as performance mustbe taken into consideration when selecting an HARQ technique, it is noteasy to determine one of the above HARQ techniques.

While the AMC and the HARQ are independent technologies for increasingadaptability to link changes, the use of them in combination canremarkably improve system performance. Once a modulation scheme and acoding rate are adaptively determined according to the downlink channelcondition by the AMC, packet data is correspondingly transmitted. If thereceiver fails to decode the packet data, it requests a retransmission.The Node B retransmits predetermined packet data by a predetermined HARQscheme in response to the retransmission request.

While the above-described schemes are applicable to HSDPA, 1×EV-DV, andEUDCH, they will be described herein in the context of channels used forHSDPA. FIG. 1 is a diagram illustrating the timing relationship betweentwo channels adopted to support HSDPA, a High Speed Shared ControlCHannel (HS-SCCH) and a High-Speed Physical Downlink Shared CHannel(HS-PDSCH). The HS-PDSCH is a transport channel for delivering packetdata from a transmitter in a Node B to a receiver in a UE, and theHS-SCCH carries control information for supporting the HS-PDSCH.

Referring to FIG. 1, the UE demodulates the HS-SCCH for a time period(HS-PDSCH) being two slots before the HS-PDSCH to acquire controlinformation necessary for demodulation of the HS-PDSCH. In FIG. 1,T_(slot) represents a time slot which is 2,560 chips. A High-SpeedDownlink Shared CHannel (HS-DSCH) is a downlink transport channel thatcarries high-speed downlink packet data. It is composed of one or moreHS-PDSCHs. The HS-PDSCH is a physical channel that delivers the HS-DSCH.

The HS-SCCH is divided into two parts each delivering controlinformation as illustrated in Table 1 below. Numerals in bracketsindicate the number of information bits.

TABLE 1 Part 1 Part 2 Channelization Code Set (7) Transport Block Size(6) Modulation Scheme (1) HARQ Process ID (3) Redundancy andConstellation Version (3) New Data Indicator (1) UE Identification (16)

The UE has to monitor up to at most four HS-SCCHs and selects one ofthem intended for the UE. Thus, if the UE determines that controlinformation has been transmitted for the UE after demodulating at mostfour the HS-SCCHs, the UE has to demodulate the HS-PDSCH. If theHS-PDSCH is not intended for the UE, the UE demodulates the nextHS-SCCHs.

The above control information delivered on the HS-SCCH illustrated inTable 1 will be described in more detail.

The Channelization Code Set (CCS) indicates the number of channelizationcodes used for the HS-PDSCH. The CCS is 7 bits and provides the numberand types of codes with which the UE performs despreading. Up to 15channelization codes are available for the HS-PDSCH according to thecurrent standards.

In HSDPA, QPSK and 16QAM are available and the Modulation Scheme (MS)indicates which is to be used. Since the CCS and the MS are requiredbefore other processes can be performed, they are set in the first partof an HS-SCCH subframe.

The Transport Block Size (TBS) indicates the size of a transport blockon a transport channel. The TBS is closely related to the MS and CCS andalso to the subject matter of the present invention, which will bedescribed later in great detail.

HARQ introduces two new schemes to increase the transmission efficiencyof Automatic Repeat reQuest (ARQ). One of them is a retransmissionrequest from a UE and a response from a Node B, and the other istemporary storage of erroneous data and combining of initialtransmission data with retransmission data.

n-channel Stop and Wait (SAW) HARQ was introduced to HSDPA to overcomethe shortcomings of a conventional SAW ARQ. The SAW ARQ does nottransmit a current data packet until an ACKnowledgement (ACK) isreceived for the previous data packet. Therefore, even though thecurrent data packet can be transmitted, the ACK for the previous datapacket has to be awaited.

In contrast, the n-channel SAW HARQ can increase channel use efficiencyby successively transmitting a plurality of data packets although an ACKfor the previous packet is not yet received. To be more specific, nlogical channels are established between the UE and the Node B and thelogical channels are identified by their specific times or channelnumbers. Thus, upon receipt of a data packet, the UE can identify thelogical channel that has delivered the data packet and take a necessaryaction such as rearranging data packets in a proper order orsoft-combines corresponding data packets. The HARQ Process ID (HAP) inTable 1 indicates a logical channel that delivers a data packet amongthe n logical channels.

The Redundancy and Constellation Version (RV) varies with a modulationscheme. The RV is given as Table 2 for 16QAM and as Table 3 for QPSK. InTables 2 and 3, X_(rv) denotes an RV coding value according toparameters s and r or parameters s, r and b. The parameters s and r areused for rate matching.

TABLE 2 X_(rv) s r b 0 1 0 0 1 0 0 0 2 1 1 1 3 0 1 1 4 1 0 1 5 0 0 2 6 10 3 7 0 1 0

TABLE 3 X_(rv) s r 0 1 0 1 0 0 2 1 1 3 0 1 4 1 2 5 0 2 6 1 3 7 0 3

The parameter b in Table 2 is information about constellationrearrangement, set forth in Table 4. Transmission is carried out in oneof the following four ways.

TABLE 4 Output bit b sequence Operation 0 s₁, s₂, s₃, s₄ None 1 s₁, s₂,s₃, s₄ Swapping MSBs with LSBs 2 s₁, s₂, s ₃, s ₄ Inversion of thelogical values of LSBs 3 s₃, s₄, s ₁, s ₂ 1 & 2

The above-described control information bits of the HS-SCCH aredependent on an ACK/Negative ACK (NACK) and a Channel Quality Indicator(CQI) transmitted from the receiver to the transmitter. In the casewhere the transmitter is to transmit a new packet in response to an ACKreceived from the receiver, the transmitter notifies the receiver that anew data packet is to be transmitted by the New Data Indicator (NDI). Atthe same time, the transmitter notifies the receiver of the RV parameterand the HAP. Also, the transmitter determines a modulation scheme andthe number of channelization codes according to a CQI received from thereceiver and notifies the receiver of the determined modulation schemeand number of channelization codes by the MS and CCS. Consequently, thecontrol information bits of the HS-SCCH are determined based on theACK/NACK and CQI received from the receiver.

This control information flow between the transmitter and the receiveris illustrated in FIG. 2. Referring to FIG. 2, at an initialtransmission, the transmitter sets the NDI to ‘NEW’ to notify thereceiver of the initial transmission. The transmitter also notifies thereceiver of the parameters s, r and b used for the transmission by theRV coding value, X_(rv). X_(rv) is selected from 0 to 7 illustrated inTable 2 or Table 3, which is expressed as ‘X_(rv)ε{0˜7}’ in FIG. 2.

After decoding a received packet, the receiver determines whether totransmit an ACK or NACK and transmits to the transmitter the ACK or NACKon a High Speed Downlink Dedicated Physical Control CHannel (HS-DPCCH).If receiving the NACK, the transmitter needs to retransmit thetransmitted packet. Hence, it sets the NDI to ‘CONTINUE’ and selects oneof X_(rv) values 0 to 7. On the other hand, upon receipt of the ACK, thetransmitter sets the NDI to ‘NEW’ and selects one of X_(rv) values 0 to7 to transmit a new packet.

Regarding the UE Identification (UE-ID), the UE is assigned up to fourHS-SCCHs, as stated earlier, and has to monitor each SCCH subframe todetect an SCCH with its UE-ID. A 16-bit UE-ID is not included as bitinformation. It is expanded to 40 bits and masked onto Part 1 after ratematching. Therefore, the UE cannot compare its UE-ID with a receivedUE-ID directly from a decoded bit sequence. It uses the UE-ID as acriterion to determine the reliability of decoding.

FIG. 3 is a block diagram of an HS-SCCH encoder for encoding controlinformation to be transmitted on the HS-SCCH. Referring to FIG. 3, anSCCH information controller 100 generates control information, i.e.X_(ms), X_(ccs), X_(tbs), X_(hap), X_(ndi), and X_(ue) representing anMS, a CCS, a TBS, an HAP, an NDI, and a UE-ID respectively, andHARQ-related information such as parameters s, r and b with which togenerate an RV.

A multiplexer (MUX) 102 multiplexes X_(ms) and X_(ccs) to X₁. An RVencoder 110 generates X_(rv) using the parameters s, r and b. A MUX 112multiplexes X_(tbs), X_(hap), X_(rv) and X_(ndi) to X₂.

A channel encoder 104 encodes X₁ to Z₁. A rate matcher 106 rate-matchesZ₁, thus outputting R₁. The channel encoder 104 uses a rate 1/3convolutional code. 8-bit Part 1 control information is extended to 40bits by channel encoding in the channel encoder 104 and rate matching inthe rate matcher 106. A UE-specific masker 108 masks R₁ with X_(ue) andthe resulting S₁ is mapped to Part 1 of the HS-SCCH by a physicalchannel mapper 120.

A UE-specific CRC attacher 114 generates a 16-bit CRC according to theUE-ID for the total sequence of Part 1 and Part 2 (X₁+X₂) received fromthe MUXes 102 and 112 and attaches the CRC to Part 2. The resulting Y isencoded in a channel encoder 116 using a rate 1/3 convolutional code. Z₂output from the channel encoder 116 is rate-matched in a rate matcher118. 13-bit Part 2 control information is extended to 80 bits by CRCaddition in the UE-specific CRC attacher 114, channel encoding in thechannel encoder 114, and rate matching in the rate matcher 118. Theoutput R₂ of the rate matcher 118 is mapped to Part 2 of the HS-SCCH bythe physical channel mapper 120.

As described before, the transmitter transmits the control informationon the HS-SCCH two slots before data transmission on the HS-PDSCH, tothereby provide information required for demodulation and decoding ofthe HS-PDSCH. The receiver demodulates the HS-PDSCH based on the controlinformation received on the HS-SCCH.

With reference to FIG. 4, a transport block used for high-speed downlinkpacket transmission in HSDPA will be described in more detail. Asillustrated in FIG. 4, the transport block includes a Media AccessControl (MAC)-hs header and MAC-hs payload. The MAC-hs payload hasMAC-hs Service Data Units (SDUs) and padding bits. The MAC-hs SDU areequivalent to MAC-d Protocol Data Unit (PDU). The size of the MAC-hsheader is variable, and the padding bits are optional in the transportblock.

The MAC-hs header includes the following fields:

-   -   Version Flag (VF): The VF field is a 1-bit flag providing        extension capabilities of the MAC-hs PDU format. The VF field        shall be set to be zero and the value one is reserved in the        current version of the protocol.    -   Queue ID: The Queue ID field provides identification of a        reordering queue in the receiver, in order to support        independent buffer handling of data belonging to different        reordering queues. The length of the Queue ID field is 3 bits.    -   Transmission Sequence Number (TSN): The TSN field provides an        identifier for the transmission sequence number on the HS-DSCH.        The TSN field is used for reordering purposes to support        in-sequence delivery to higher layers. The length of the TSN        field is 6 bits.    -   Size Index Identifier (SID): The SID field identifies the size        of a set of consecutive MAC-d PDUs. The MAC-d PDU size for a        given SID is configured by higher layers is independent for each        Queue ID. The length if the SID field is 3 bits.    -   Number of MAC-d PDUs (N): The number of consecutive MAC-d PDUs        with the same size is identified with the N field. The length of        the N field is 7 bits. In Frequency Division Duplex (FDD) mode,        the maximum number of PDUs transmitted in a single Transmission        Time Interval (TTI) shall be assumed to be 70.    -   Flag (F): The F field is a flag indicating if more SID fields        are present or not. If the F field is set to ‘0’, the field is        followed by an additional set of SID, N and F fields. If the        field is set to ‘1’, the F field is followed by a MAC-d PDU.

The padding bits in the MAC-hs payload of the transport block areoptionally included to match the transport block size and they do notprovide any information. As far as the information bits are concerned,the padding bits are unnecessary.

When the transport block is mapped to a physical channel, the additionof unnecessary the padding bits to the transport block leads to a lowercoding rate than without the padding bits. Hence, if the transport blockis without the padding bits, the resulting increase in coding rateincreases throughput.

In this case, the transport block size is changed by as many bits as thenumber of the padding bits, and thus different from the TBS known to thereceiver. Hence, the size of the changed transport block must be sent tothe receiver, with additional information bits.

Considering that the HSDPA channel is transmitted every 2 ms, however,the notification is not easy. It is preferable to inform the receiver ofthe transport block size in which the number of padding bits is takeninto account without additional information bits. Also, since channelencoding is performed on a transport block without the padding bits, thechannel decoder of the receiver has to decode a received transportchannel correspondingly. That is, the receiver has to perform de-ratematching and channel decoding according to the size of a transport blockrate-matched and channel-encoded in the transmitter.

SUMMARY OF THE INVENTION

An object of the present invention is to substantially solve at leastthe above problems and/or disadvantages and to provide at least theadvantages below. Accordingly, the present invention provides atransmitting and receiving apparatus and method for preventing a codingrate decrease caused by the presence of padding bits in a transportblock in order to increase system throughput in a wireless packet datacommunication system.

The present invention also provides a transmitting and receivingapparatus and method for transmitting a transport block without paddingbits, thereby increasing a coding gain by as much as the number of theeliminated padding bits and thus increasing system throughput in awireless packet data communication system.

The present invention also provides a transmitting and receivingapparatus and method for transmitting a transport block without paddingbits and notifying the receiving apparatus of the number of theeliminated padding bits without additional information bits in awireless packet data communication system.

The present invention also provides a transmitting and receivingapparatus and method for transmitting a transport block without paddingbits after transport channel encoding, along with information indicatingthe number of the padding bits from the transmitting apparatus, andextracting the padding bit number information from received controlinformation, transport channel-decoding the transport block without thepadding bits, taking into account the number of the padding bits, andthus extracting information bits in the receiving apparatus.

The present invention provides a transmitting and receiving apparatusand method for transmitting additional control information about thenumber of padding bits without an additional information bit field byefficiently utilizing an existing control information field.

According to an aspect of the present invention, in a wireless packetdata transmitter for transmitting data packet on a transport channel andcontrol information for supporting the transport channel on a controlchannel to a wireless packet data receiver in a wireless packet datacommunications system, optional padding bits are eliminated from atransport block for data packet transmission. The transport blockwithout the padding bits is transport channel-encoded and transmitted onthe transport channel. Control information including a padding bitnumber indicator indicating the number of the eliminated padding bits iscontrol channel-encoded and transmitted on the control channel.

According to another aspect of the present invention, in a wirelesspacket data receiver for receiving data packet on a transport channeland control information for supporting the transport channel on acontrol channel from a wireless packet data receiver in a wirelesspacket data communications system, control channel-encoded controlinformation is received on the control channel and controlchannel-decoded. Transport block size information included in thecontrol channel-decoded control information is corrected based on apadding bit number indicator included in the control channel-decodedcontrol information. A transport channel-encoded transport block withoutpadding bits is received on the transport channel and transportchannel-decoded according to the corrected transport block size.

If the wireless packet data communication system is HSDPA, thetransmitter transmits the padding bit indicator in a redundancy andconstellation version (RV) field configured for the transmission of theRV information, instead of the RV information, if the transport block isan initial transmission block carrying a new data packet. If thetransport block is a retransmission block carrying a retransmission datapacket, the transmitter selects one of the predetermined RV codingvalues and transmits in the RV field the selected RV coding value as theRV information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a diagram illustrating the timing relationship between anHS-SCCH and its associated HS-PDSCH in HSDPA;

FIG. 2 is a diagram illustrating a flow of control information between atransmitter and a receiver in a typical HSDPA system;

FIG. 3 is a block diagram of an HS-SCCH encoder in a packet datatransmitter in the typical HSDPA system;

FIG. 4 illustrates the structure of a transport block for delivering ahigh-speed downlink packet;

FIG. 5 is a block diagram of an HS-SCCH encoder in a packet datatransmitter in a HSDPA system according to the present invention;

FIG. 6 is a block diagram of an HS-PDSCH encoder in the packet datatransmitter in the HSDPA system according to the present invention;

FIG. 7 is a block diagram of a packet data receiver in the HSDPA systemaccording to the present invention; and

FIG. 8 is a flowchart illustrating an operation of a control informationinterpreter according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the followingdescription, well-known functions or constructions are not described indetail since they would obscure the invention in unnecessary detail.

FIGS. 5 and 6 are block diagrams of an HS-SCCH encoder as a controlchannel encoder and an HS-PDSCH encoder as a transport channel encoderin a packet data transmitter in a HSDPA system according to the presentinvention. In the illustrated cases of FIGS. 5 and 6, the presentinvention is implemented in the context of HSDPA.

Referring to FIG. 6, the HS-PDSCH encoder eliminates optional paddingbits from a transport block carrying packet data and encodes thetransport block without the padding bits (transport channel encoding orHS-PDSCH encoding), prior to transmission on the HS-PDSCH. According tothe present invention, the HS-PDSCH encoder further includes a paddingbit eliminator 300 in addition to the components of a typical HS-PDSCHencoder, i.e. a CRC attacher 302, a channel encoder 304, a rate matcher306, a physical channel segmenter 308, an HS-DSCH interleaver 310, aconstellation rearranger for 16QAM 312, and a physical channel mapper314.

A transport block having the configuration illustrated in FIG. 4 isprovided to the padding bit eliminator 300 from a MAC layer (not shown).If the transport block includes padding bits, the padding bit eliminator300 eliminates the padding bits and provides the resulting transportblock to the CRC attacher 302. Subsequently, the transport block withoutthe padding bits is HS-PDSCH-encoded and transmitted on physicalchannels PhCH#1 to PhCH#P. The HS-PDSCH-encoding is performed in ageneral way through the CRC attacher 302, the channel encoder 304, therate matcher 306, the physical channel segmenter 308, the HS-DSCHinterleaver 310, the constellation rearranger 312, and the physicalchannel mapper 314. Thus, its detailed description is not providedherein.

Referring to FIG. 5, the HS-SCCH encoder includes a Padding Bit NumberIndicator indicating the number of the eliminated padding bits in thecontrol information and encodes the control information (control channelencoding or HS-SCCH encoding), prior to transmission on the HS-SCCH.

Table 5 below lists control information bits transmitted on the HS-SCCHaccording to the present invention which is implemented in HSDPA.Numerals in the brackets denote the number of information bits.

TABLE 5 Part 1 Part 2 Channelization Code Set (7) Transport Block Size(6) Modulation Scheme (1) HARQ Process ID (3) Redundancy andConstellation Version (3)/Padding Bit Number Indicator (3) New DataIndicator (1) UE Identification (16)

Table 5 is the same as Table 1 illustrating the configuration of controlinformation recommended by the present standards, in that Part 1includes the CCS and MS and Part 2 includes the TBS, HAP, RV, NDI, andUE-ID but different from Table 1 in that the RV field is modified toadditionally have the Padding Bit Number Indicator.

If one of the RV coding values, X_(rv) 0 to 7 is preset as a default forinitial transmission between the transmitter and the receiver, there isno need for transmitting X_(rv) at an initial transmission. Thetransport block size is equal for initial transmission andretransmission.

Hence, the HS-SCCH encoder transmits the Padding Bit Indicator in the RVfield instead of RV information at an initial transmission, andtransmits an RV coding value, X_(rv) in the RV field at aretransmission.

The receiver determines that information received in the RV field at theinitial transmission is the Padding Bit Number Indicator, not X_(rv).The receiver determines the number of padding bits eliminated by thetransmitter from the Padding Bit Number Indicator, and considers X_(rv)to be the default value. At the retransmission, the receiver recognizesthe information received in the RV field as X_(rv) as usual. Since thesame transport block size is used at the initial transmission and theretransmission, the number of padding bits eliminated in the transmitteris not changed. Accordingly, the receiver has knowledge of the number ofeliminated padding bits achieved at the initial transmission, withoutreceiving the Padding Bit Number Indicator at the retransmission.

The maximum number of retransmissions is 4 or 8 for HARQ and the orderof the RV coding values is not defined in the current standards. Giventhe maximum number of retransmissions=8, each of X_(rv) values 0 to 7shown in Table 2 or Table 3 cannot be used even once, or can be used upto eight times. In the case where the receiver transmits an NACKcontinuously, X_(rv) can be used as follows.

TABLE 6 Initial transmission X_(rv) = 0 1^(st) retransmission X_(rv) = 12^(nd) retransmission X_(rv) = 2 3^(rd) retransmission X_(rv) = 3 4^(th)retransmission X_(rv) = 4 5^(th) retransmission X_(rv) = 6 6^(th)retransmission X_(rv) = 7 7^(th) retransmission X_(rv) = 2where X_(rv)=5 is not used even once and X_(rv)=2 is used twice.

In another example,

TABLE 7 Initial transmission X_(rv) = 0 1^(st) retransmission X_(rv) = 02^(nd) retransmission X_(rv) = 0 3^(rd) retransmission X_(rv) = 0 4^(th)retransmission X_(rv) = 0 5^(th) retransmission X_(rv) = 0 6^(th)retransmission X_(rv) = 0 7^(th) retransmission X_(rv) = 0where X_(rv)=0 is used for all transmission and retransmissions.

If the number of retransmissions is 8, it is preferable to use the RVcoding values, X_(rv) 0 to 7 each once.

TABLE 8 Initial transmission X_(rv) = 0 1^(st) retransmission X_(rv) = 12^(nd) retransmission X_(rv) = 2 3^(rd) retransmission X_(rv) = 3 4^(th)retransmission X_(rv) = 4 5^(th) retransmission X_(rv) = 5 6^(th)retransmission X_(rv) = 6 7^(th) retransmission X_(rv) = 7

Considering the parameters s, r and b, it is preferred that X_(rv) isset to 0 at an initial transmission. Thus, the default RV coding valuepreset between the transmitter and the receiver for the initialtransmission is preferably 0.

The HS-SCCH encoder of FIG. 5 thus transmits the RV coding value X_(rv)or the Padding Bit Number Indicator in the RV field according to theNDI, X_(ndi). Compared to the HS-SCCH encoder of FIG. 3, the HS-SCCHencoder of the present invention further includes a switch 222 forswitching one of the RV coding value X_(rv) from an RV encoder 210 andthe Padding Bit Number Indicator, X_(pd) according to the NDI, X_(ndi)to a MUX 212.

At an initial transmission, the transmitter sets X_(ndi) to ‘NEW’. Thenthe switch 222 switches X_(pd) to the MUX 212. Thus, X_(pd) istransmitted in the RV field. Since X_(rv) is a default value of 0 at theinitial transmission, there is no need for transmitting X_(rv).

At a retransmission, the transmitter sets X_(ndi) to ‘CONTINUE’. Thenthe switch 222 switches X_(rv) to the MUX 212. Thus, X_(rv) istransmitted in the RV field, as is the general case. Since X_(pd) is thesame in both the initial transmission and the retransmission, it istransmitted only once at the initial transmission.

Except for the fact that either X_(rv) or X_(pd) is transmitted in theRV field depending on initial transmission or retransmission, theHS-SCCH encoder of FIG. 5 is identical to that of FIG. 3. Therefore, theother components that is, an SCCH information controller 200, MUXes 202and 212, a UE-specific CRC attacher 214, channel encoders 204 and 216,rate matchers 206 and 218, a UE-specific masker 208, and a physicalchannel mapper 220 are basically the same as their counterparts in FIG.3 in configuration and perform HS-SCCH encoding in the same manner.

FIG. 7 is a block diagram of a packet data receiver in the HSDPA systemaccording to the present invention. Referring to FIG. 7, an HS-SCCHdecoder 400 as a control channel decoder decodes control informationreceived on the HS-SCCH (control channel decoding or HS-SCCH decoding),thereby extracting control information parameters illustrated in Table5. A control information interpreter 402 corrects a TBS based on aPadding Bit Number Indicator included in the decoded controlinformation.

The operation of the control information interpreter 402 will bedescribed with reference to FIG. 8. In FIG. 8, upon receipt of theHS-SCCH at the UE in step 500, the HS-SCCH decoder 400 provides decodedcontrol information to the control information interpreter 402. In step502, the control information interpreter 402 determines whether an NDIvalue, X_(ndi) is ‘NEW’ or ‘CONTINUE’. If X_(ndi) is ‘CONTINUE’, thecontrol information interpreter 402 considers that X_(rv) is in an RVfield is X_(rv) and stores X_(rv) together with the other controlinformation parameters, as is the usual case, in step 506.

On the other hand, if X_(ndi) is ‘NEW’, the control informationinterpreter 402 considers that X_(pd) is in the RV field and corrects aTBS by subtracting a Padding Bit Number Indicator X_(pd) from the TBSX_(tbs) in step 504. The corrected TBS represents the size of atransport block without padding bits. At the same time, X_(rv) isdecided as 0. In step 506, the corrected TBS, X_(tbs) and the RV codingvalue, X_(rv) are stored together with the other control informationparameters.

The control information interpreter 402 provides the above controlinformation to a HS-PDSCH decoder 404 for decoding the HS-PDSCH. TheHS-PDSCH decoder 404 HS-PDSCH-decodes an HS-PDSCH-encoded transportblock without padding bits received on the HS-PDSCH through de-ratematching and channel decoding in accordance with the corrected TBS.

In accordance with the present invention as described above, as theamount of packet data actually transmitted on a transport channel isreduced by as many bits as the number of eliminated padding bits, thenumber of punctured bits during rate matching is decreased. Therefore, acoding gain corresponding to the number of the padding bits is achievedand thus system throughput is increased. Furthermore, information aboutthe number of the padding bits can be transmitted without an additionalinformation bit field through efficient use of an existing controlinformation field.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, they are mere exemplaryapplications. While the present invention is implemented in HSDPA inthese embodiments, it is also applicable to 1×EV-DV. Besides downlinkpacket data transmission, the present invention can be applied to uplinkpacket data transmission like EUDCH in the same manner. Therefore, itwill be understood by those skilled in the art that various changes inform and details may be made therein without departing from the spiritand scope of the invention as defined by the appended claims.

1. A wireless packet data transmitter for transmitting to a wirelesspacket data receiver data packet on a transport channel and controlinformation for supporting the transport channel on a control channel ina wireless packet data communications system, comprising: a padding biteliminator for eliminating optional padding bits of a variable size froma transport block for data packet transmission; a transport channelencoder for transport channel-encoding the transport block without thepadding bits and transmitting the encoded transport block on thetransport channel; and a control channel encoder for controlchannel-encoding the control information including a padding bit numberindicator indicating the number of the eliminated padding bits andtransmitting the encoded control information on the control channel,wherein if the transport block is an initial transmission block carryinga new data packet, the control channel encoder transmits the padding bitnumber indicator in a redundancy and constellation version (RV) field,and if the transport block is a retransmission block carrying aretransmission data packet, the control channel encoder selects one ofpredetermined RV coding values and transmits the selected RV codingvalue in the RV field.
 2. The wireless packet data transmitter of claim1, wherein the wireless packet data communications system is a highspeed downlink packet access (HSDPA) system, the transport channel is ahigh speed physical downlink shared channel (HS-PDSCH), and the controlchannel is a high speed shared control channel (HS-SCCH).
 3. Thewireless packet data transmitter of claim 1, wherein an RV coding valuepreset between the wireless packet data transmitter and the wirelesspacket data receiver among the RV coding values is selected as a defaultat initial transmission.
 4. The wireless packet data transmitter ofclaim 3, wherein the RV coding value selected as the default is
 0. 5.The wireless packet data transmitter of claim 1, wherein the transportchannel encoding includes rate matching and channel encoding.
 6. Amethod of transmitting to a wireless packet data receiver data packet ona transport channel and control information for supporting the transportchannel on a control channel in a wireless packet data communicationssystem, comprising: eliminating optional padding bits of a variable sizefrom a transport block for data packet transmission; transportchannel-encoding the transport block without the padding bits andtransmitting the encoded transport block on the transport channel; andcontrol channel-encoding the control information including a padding bitnumber indicator indicating the number of the eliminated padding bitsand transmitting the encoded control information on the control channel,wherein control channel encoding comprises: transmitting the padding bitnumber indicator in a redundancy and constellation version (RV) field,if the transport block is an initial transmission block carrying a newdata packet; and selecting one of predetermined RV coding values andtransmitting the selected RV coding value in the RV field, if thetransport block is a retransmission block carrying a retransmission datapacket.
 7. The method of claim 6, wherein the wireless packet datacommunications system is a high speed downlink packet access (HSDPA)system, the transport channel is a high speed physical downlink sharedchannel (HS-PDSCH), and the control channel is a high speed sharedcontrol channel (HS-SCCH).
 8. The method of claim 6, wherein apredetermined RV coding value among the RV coding values is selected asa default at the initial transmission.
 9. The method of claim 8, whereinthe RV coding value selected as the default is
 0. 10. The method ofclaim 6, wherein the transport channel encoding step comprises transportchannel-encoding the transport block without the padding bits throughrate matching and channel encoding.